Mopidralazine is slower in onset and longer lasting than hydralazine and is devoid of adrenergic system stimulation. Its antihypertensive action is mediated by arteriolar dilatation. In the rat, Mopidralazine is rapidly metabolized, mainly by pyrrole-ring opening and subsequent formation of a mesoionic 3-(1-pyridazinyl)pyridazine In dogs, oxidative cleavage of the morpholine ring has been found to be the primary metabolic attack. In a small clinical trial, Mopidralazine resulted in significant reductions in blood pressure, both supine and standing, which was maximal 4-8 h after dosing, with no additional orthostatic component.